Effect Of Carbon Containing Magnesium Aluminate Spinel Composite Powders On Properties Of Low-carbon Spinel-C Composite Refractories

Magnesium-aluminum spinel-carbon composite refractories are suitable for"three main products"slag zone and monolithic stopper for continuous casting of special steel types such as high manganese steel due to their excellent thermal shock resistance and slag corrosion resistance.As industries such as iron and steel metallurgical tend to become more efficient and clean,higher requirements are imposed on the monolithic stopper for continuous casting,such as thermal shock resistance and slag corrosion resistance.The development of low-carbon stopper is not only of practical significance for improving the quality and efficiency or environmental protection of resources of the iron and steel metallurgical industry,but also an important way to improve the anti-scour performance and extend the service life of the stopper.Directly reduce the amount of flake graphite in traditional carbon-containing refractories,which reduces the thermal shock resistance and slag corrosion resistance of the refractories.At present,in addition to adjusting the content and grain size of different antioxidants to optimized the performance of low-carbon refractories,researchers have mainly explored the evolution of the microstructure of low-carbon refractories from the aspects of composite of additives and introduction of nano-carbon sources.While improving the oxidation resistance of low-carbon and carbon-containing refractories,it also improves its resistance to slag corrosion and mechanical properties.Although nano-carbon has obvious effects on improving the thermal shock resistance of low-carbon refractories,there are hard problems that are difficult to disperse,high cost,and easily oxidized.The preparation of carbon-containing composite powders and its application to carbon-containing refractories are expected to solve the above problems.In the present work,the effect of graphite content on the properties of spinel-carbon refractories was first studied,and then a carbon containing magnesium aluminum spinel composite powders（C/MgAl₂O₄）was prepared by inert atmosphere protection sintering method.Study on composite powders on properties of low carbon MgAl₂O₄-C refractories.And the micro-analysis of the monolithic stopper sample which adding the composite powders.The main conclusions are as follows:（1）With the gradual decrease in the amount of graphite,the thermal shock resistance and oxidation resistance of MgAl₂O₄-C refractories first increase and then decrease.When the graphite content is 6wt.%,The residual strength ration of MgAl₂O₄-C refractory is 40%,which is 24%higher than that of the sample containing 10wt.%graphite.Moreover,when the graphite content is 6wt.%,the hot modulus of rupture and cold crushing strength of the sample are improved obviously.This is because when the graphite content is adjusted,the flake graphite fills the aperture of the sample,which effects the apparent porosity and bulk density of the sample.In addition,because of the difference in coefficient of thermal expansion between flaky graphite and magnesia-alumina spinel,too much flaky graphite will cause micro-cracks inside the sample and damage the mechanical properties of the sample.（2）The addition of C/MgAl₂O₄ composite powders improves the mechanical properties and functional performance of low-carbon MgAl₂O₄-C refractories.The main reason is that the addition of C/MgAl₂O₄ composite powders with a wide particle size distribution not only improves the apparent porosity of the spinel-carbon sample,but also increases the strength of the sample.Moreover,the better oxidation resistance and the unique structure improve the thermal shock resistance and slag corrosion resistance of the sample.（3）The large-scale preparation technology of the C/MgAl₂O₄ composite powders has been developed and added to the head of monolithic stopper,which can effectively improve the slag corrosion resistance of the stopper.Microscopic analysis shows that,the C/MgAl₂O₄ composite powders was uniformly distributed in the stopper matrix,forming a meshy form to capture the slag,and solid solution the slag into independent high viscosity circular regions,restrict the slag to further penetrate the stopper.In addition,the more evenly distributed nano-carbon also reduce the wetting property of the stopper to the slag,and improves the slag corrosion resistance of the monolithic stopper.